1. Field of the Invention
The present invention relates to an image processing apparatus and a control method thereof.
2. Description of the Related Art
Image display apparatuses in which a stereoscopic video image is obtained by displaying an image for right eye and an image for left eye have become more commonplace in recent years. This has driven the need for video production compatible with stereoscopic video.
In one video production technique, contrast sensation is improved by obtaining a gradation correction curve (γ curve) according to a statistic, such as an image brightness histogram, for each frame, and by correcting pixel value gradation on the basis of the gradation correction curve (γ correction process). In another technique (local γ correction process), the γ curve is different for each pixel in the image (Japanese Patent Application Publication No. 2004-287794).
The technique disclosed in Japanese Patent Application Publication No. 2004-287794 realizes local γ correction by dividing an image into a plurality of regions and, for each pixel, combining a reference γ correction parameter, obtained at each region, on the basis of the coordinates of the pixel to be corrected.
However, in techniques such as the one disclosed in Japanese Patent Application Publication No. 2004-287794, an image is divided into a plurality of regions, and a local γ correction process that employs a γ curve obtained for each region is used, as-is, for an image for left eye and an image for right eye of a stereoscopic video image. Problems may arise thereupon on account of the particular characteristics of the stereoscopic video image. In a stereoscopic video image, specifically, a same object stands at dissimilar positions in an image for left eye and an image for right eye. When dividing an image into a plurality of regions and obtaining a γ curve for each region, specifically, a same object may belong to regions at different positions in the image for left eye and the image for right eye. In such a case, the image data in the divided region is dissimilar for the image for left eye and the image for right eye, and hence the γ curves obtained for each region are likewise dissimilar. As a result, dissimilar γ curves are used, for a same object, in the image for left eye and the image for right eye, whereupon the stereoscopic sensation is lost and flicker occurs.